桩式离岸堤保滩促淤工程消浪效果试验研究

在上海奉贤南北港保滩促淤工程中，采用了一种新型结构型式－桩式离岸堤，并通过物理模式试验进行了桩式离岸堤消浪效果研究。针对离岸堤通常建于近岸水区破波带的特点，重点研究水深，堤高以及堤身结构对波浪衰减的影响，同时对桩式离岸堤堤后水域的波浪底流速 分析探讨。研究结果表明，桩式离岸堤不仅具有良好的消浪效果。而且可在较大范围内改变波态，即由引起水体剧烈紊动的破波转变为浅水推进波，从而有效地改善海滩上的动力条件，促进海滩免受侵蚀，是一种具有广泛应用前景和新型保滩促淤结构。     

光生物反应器中光衰减特征与螺旋藻生长动力学研究

分析了光照强度在光生物反应器中的分布特征，结果表明，当光波长及光传播的路径确定时，光生物反应器中光衰减特征主要受培养物生物量浓度的影响，由回归的模型对实验数据的拟合可分析光衰减特征与培养物生物量浓度的相关性，为光生物反应器中平均光照强度的确定奠定基础。在光生物反应器中，当营养底物和环境温度不是螺旋藻生长限制因子时，通过平均光照强度对螺旋藻比生长速率的影响分析，结果表明，在实验条件下，螺旋藻比生长速率与平均光照强度的动力学模型可用Aiba光生长抑制方程描述，光亲和系数Ks为238.29umol/(m^2.s)，光抑制系数Ki为0．00493s.m^2/umol，光生物反应器中螺旋藻生长的饱和光照强度出现在190－272umol/(m^2.s)的范围内。     

Dynamics and control of a towed underwater vehicle system, part I: model development

Autonomous vehicles are being developed to replace the conventional, manned surface vehicles that tow mine hunting towed platforms. While a wide body of work exists that describes numerical models of towed systems, they usually include relatively simple models of the towed bodies and neglect the dynamics of the towing vehicle. For systems in which the mass of the towing vehicle is comparable to that of the towed vehicle, it becomes important to consider the dynamics of both vehicles. In this work, we describe the development of a numerical model that accurately captures the dynamics of these new mine hunting systems. We use a lumped mass approximation for the towcable and couple this model to non-linear numerical models of an autonomous surface vehicle and an actively controlled towfish. Within the dynamics models of the two vehicles, we include non-linear controllers to allow accurate maneuvering of the towed system.     

Seasonal dynamics in pelagic fish abundance in a Baltic Sea coastal area

The spring-spawning Baltic Sea herring spawn in coastal areas that also serve as nursery areas for the young fish during their first summer. In a bay known as a herring spawning and nursery area, the pelagic fish abundance was quantified using hydroacoustics every second week from late spring to autumn in 2000 and 2001. A dense system of survey transects allowed determination of the acoustic index (the nautical area scattering coefficient) for fish abundance with high precision. The variation, expressed as the geostatistical coefficient of variation, was on average 5% both years and ranged from 3–11% (2000) and 3–8% (2001). Through the hydroacoustic data intra-annual dynamics in acoustic fish abundance, densities and size composition could be followed, which showed similar trends in both years. In spring and early summer acoustic fish densities were low, followed by a drastic, 20-fold increase in late summer. Hydroacoustic data and biological samples suggest that the increase was caused mainly by the recruitment of young-of-the-year herring to the acoustically assessable pelagic fish community. This age class is commonly not well represented in catches when using traditional sampling gears such as gill nets and trawls, and hydroacoustics may help to improve quantitative estimates of small juvenile fish in order to increase the understanding of biological processes in coastal nursery areas.     

Influence of large-diameter pipe pile driving on surrounding marine soils and adjacent submarine pipelines

Abstract

With the large-scale development and utilization of ocean resources and space, it is inevitable to encounter existing submarine facilities in pile driving areas, which necessitates a safety assessment. In this article, by referring to a wharf renovation project as a reference, the surrounding soil response and buried pipe deformation during pile driving in a near-shore submarine environment are investigated by three-dimensional (3D) numerical models that consider the pore water effect. Numerical studies are carried out in two different series: one is a case of a single pile focusing on the effect of the minimum plane distance of the pile–pipe, and the other is a case of double piles focusing on the effect of the pile spacing.     

Eddy Diffusion Coefficients of Suspended Particulate Matter: Effects of Wind Energy Transfer and Stratification

Gross sedimentation rates (GSR) have been measured using sediment traps placed at nine different levels above the bed (0·3, 0·5, 0·8, 1·0, 2·0, 4·0, 6·0, 8·0 and 10·0 m). The sediment traps were deployed for 1·25 years and recovered 28 times during the study period. Low average GSR values of 5·5 g m^-2 day^-1 were obtained at 10·0 m, and high average GSR values of 114·8 g m^-2 day^-1 were obtained at 0·3 m. An expression for the eddy diffusion coefficient of suspended particulate matter (K_s), based on the measured GSR is given. The expression has been used for modelling of K_s at the different trap levels above the bed. High values (≈42 cm² s^-1) of K_s were obtained at the upper traps, whereas low values (≈2 cm² s^-1) were obtained near the bed. Comparison between level of turbulent energy in terms of shear stress at the boundaries of the water column, i.e. from the wind and the bed flow, showed that wind energy exceeded that of the bed flow by a factor 16. At 5·0 m K_s was positively correlated (r=0·66) to the eddy diffusion coefficient of momentum (K_m) derived from the wind energy transfer to the water, giving an average β of 0·5 for K_s =βK_m. The density difference between surface and bottom waters has been designated a parameter of stratification, and is discussed in relation to variations of K_s and K_m .